SB 741 
.F6 H4 
Copy 1 



WISCONSIN 



^V# ftorUciltnral Soe^ 



BULLETIN NO. 5 



Published by authority of the Executive Committee 



m 



fire: blight 



MADISON, WIS., MAY, I905 



The Bulletins and Annual Reports of this Society are sent 
free to mennbers of the Society 



a' 



^tA^K 



<( 



w 



Wisconsin State Horticultural Society 



OFFICERS. 

T. E. Loope, President Eureka 

Geo. J. Kellogg, Vice-President Lake Mills 

F. Cranefield, Secretary Madison 

L. G. Kellogg, Treasurer. Ripon 

BOARD OF iVlANAGERS. 
T. E. Loope. L. G. Kellogg. F. Cranefield. 



The Bulletins of the Society are sent free to members. Persons 
not members may obtain copies until the editions are exhausted on 
application to the Secretary. 



0. OF D, 
JUN 7 1913 



INTRODUCTION 



The disease affecting apple and pear trees known as Fire Blight 
has been discussed in this Society for 35 years according to the 
Annual Reports. 

During this time about every member in regular attendance at 
the meetings has had a turn at "blight," but it still remains to vex 
the orchardists of the state, professional as well as amateur. That 
the disease is still prevalent is shown by the numerous inquiries 
received at this office. In order to reply conveniently to these ques- 
tions it was thought best to issue a pamphlet giving a brief history 
and description of the disease as well as approved remedies. In 
looking over the literature on the subject a press bulletin by Prof. 
Henderson of the Idaho Experiment Station seemed to afford the 
desired information presented clearly and concisely and it is hereby 
reproduced by courtesy of Director H. T. French of the Idaho Station. 

F. Cranefield, Editor. 



UNIVERSITY OF IDAHO 

AGUICULTURAL. EXPERIMENT STATION 

MOSCOW, IDAHO: 

L. F. HENDERSON, Botanist 



fire: bliqht 



A Bacterial Disease of the Pear and the Apple. 



Spring is now upon us, — the time when the careful horticulturist 
must be preparing to combat those many ills incident to fruit cul- 
ture, whether of an insect or of a fungous nature. Of all these prob- 
ably the Fire Blight is the worst and most to be dreaded. 

The name "Fire Blight" is the proper one to use; it should not 
be called "Pear Blight" for two reasons. In the first place it is lia- 
ble to be confused with the Pear-leaf Blight, a disease which attacks 
the leaf of the pear, and incidentally injures the fruit. In the next 
place this disease is not limited to- the pear; it is fast becoming too 
common on the apple as well, in our state. Nay. in many states it 
attacks all of the pomaceous fruits, such as pear, apple, quince, crab 
and hawthorn. 

HISTORICAL. 

Though this trouble has been known -as working havoc in orchards 
for a century or more, it is only in comparatively recent times that 
its true nature has been well understood. For a long period of years 
the discussions of this trouble were of such a theoretic nature that 
many horticultural societies forbade its being brought up in their 
meetings, unless someone had something of absolute knowledge to 
offer about it. Various causes were ascribed for its presence, such 
as "sour sap," "atmospheric conditions," "soil conditions," and "ef- 
fects of various fungi." In 1878, however. Professor Burrill of Illi- 
nois discovered the true cause and announced his discovery to the 
world. This was found to be a bacterial disease, due to the pres- 
ence of myriads of little germs in the inner bark and cambium. The 
germ was called by Prof. Burrill Micrococcus amyiovorus from the 
eagerness with which it seizes upon and devours the starch in these 



Wisconsin State Horticultural Society 



tissues. From the subsequent studies of Arthur at the Geneva Sta- 
tion in New York, and of Waite in the U. S. Department of Agri- 
culture, we know how this germ or bacterium lives, reproduces itself 
and is carried from tree to tree. 

APPEARANCE OF BLIGHT. 

Luckily the disease is a very conspicuous one, which renders its 
presence in an orchard the more inexcusable when well known. It 
affects, twigs, leaves, young fruit, and even the branches or trunks. 
From the experiments of Waite it has been found that it cannot 
attack the plant through the uninjured bark or leaf. It can, however, 
gain entrance through any injured place on trunk, limb or even leaf. 
Its most common points of entrance are natural ones. These are 
the young growing tips of the branch, the stigma of the flower, or 
the glands which secrete nectar. Therefore the "flower-blight," the 
"twig-blight" and the "branch or trunk blight" are all forms of this 
disease. 

In the first, the young twig, especially if it be growing rapidly, 
turns black in both leaf and stem, and wherever the leaves are 
blighted they remain black and dead through the ensuing winter. 
This black, piratical flag is the surest evidence of its presence. 

In the "flower-blight" a whole bunch of flowers, or frequently 
every bunch on the tree will be affected, and dying back to the be- 
ginning of the spur, hold the blackened flowers and young fruit also 
through the entire year. This is the most common form on the apple. 

Frequently an entire limb or even the trunk will be affected for 
only a short distance, while the top will still be entirely free from 
the disease, and this can only be understood when we speak of how 
the disease is spread. 

More frequently upon the pear several limbs and even the whole 
trunk will be affected, and when this is the case the tree should be 
cut out root and branch. 

MEANS OF DISSEMINATION. 

If the young shoots of a tree affected with blight be examined, 
small drops of sticky, thick fluid will be found exuding from the 
edge of the diseased area. If one of these drops be examined with 
a high power of a microscope, myriads of little oblong bodies will 
be seen, some separate, some in short chains. These are bacteria. 
Arthur proved that these bodies, inoculated into a sound tree by a 
needle, would produce the disease; Waite proved to us beyond dis- 
pute that insects, especially bees, are the main instruments in their 
dissemination. They are attracted by the viscid sap, suck up part 
or all of the drop, and then carry thousands of these germs with 
them to innoculate flowers, shoots, or wounded places in the bark. 
Undoubtedly heavy currents of wind assist in spreading the disease 
and probably account for the commonness of "twig blight." The 



Fire Blight 



question comes right here: Shall I keep bees if I have an orchard? 
Certainly, and for two reasons. First, the honey, and the revenue 
derived from it, are often no small object to the farmer. Second, 
the bees are absolutely needed to assist in proper cross-fertilization 
or pollination of the flowers. This leads us to the subject of reme- 
dies, for preventives there are none. 



REJVIEDIES. 

As soon as the bacteria are carried to young flower or wound, 
they effect entrance, and living upon the sap and starch, multiply 
rapidly. If they gain entrance along a limb or trunk, they live in 
the inner bark and cambium-layer, — that layer which adds yearly 
to the growth of both bark and wood. 

It can readily be seen from this that they are well covered, and 
consequently spraying does no good. The only remedy thus far 
found has been and is the careful and continuous use of the saw and 
pruning knife. All diseased shoots and limbs should be cut off at 
from 6 inches to one foot below the place of evident infection or 
injury, as the bacteria have always gone down deeper into the limb 
than seems to be the case from the outside. Many pruners have the 
habit of splitting down he bark to see how far the disease has pro- 
ceeded, but this practice is to be condemned, as they never can see 
how far the disease has proceeded, and the incision of the knife may 
carry the bacteria from diseased to healthy tissues. If the blight is 
bad in either the pear or apple-orchard, the knife or saw should be 
sterilized each time it is used, by either passing it through a flame, 
or dipping it into weak carbolic-acid water, or into kerosene. The 
pruned limbs or fragments should be collected and burned and both 
pruning and burning should be done mainly in the dormant season, 
before the sap has started, the bacteria have awakened, and the 
bees are visiting the orchard. This is the best time for pruning and 
burning, but not the only one; it should be done whenever the dis- 
ease makes its appearance. All large wounds should be painted over 
with paint as soon as the tree is trimmed, to prevent the re-inocu- 
lation through the exposed tissues. Where the blight is bad, even 
young shoots or water-sprouts should have their cut bases painted, 
for it has been known time and again that the limbs and even trunks 
have been innoculated through these cut stubs. 

The pear is much more easily pruned for this disease than is the 
apple. On the former it commonly manifests itself in dead or dying 
shoots, limbs, or trunks, which can readily be cut away below the 
progress of the disease. On the apple, however, it is commonly the 
shoots all over the tree, and especially the fruit spurs and their clus- 
ters of flowers, which are most affected. Pruning here becomes a 
much more difficult and even serious undertaking. Where only a few 
shoots and fruit spurs are affected these can be cut away close to 
the tree, and the wound immediately covered with paint. Where, 
however, almost all of the fruit spurs on the whole tree have died, 



015 793 597 5 



Wisconsin State Horticultural Society 



the best way is to cut off entire and large limbs, cover the wounds 
with paint, and stimulate the production of new shoots and subse- 
quent fruit spurs. In one place my attention was called to a very 
interesting though sad evidence of the efficacy of bees in spreading 
the disease. All the splendid large apple trees near the hives were 
without exception seriously injured by blight, while as we proceeded 
on radii from the hives the blight grew less and less, and almost 
disappeared on the edge of the orchard farthest from the hives. 

OTHER HELPS. 



It has been often noticed that rapidly growing trees are more 
subject to blight than slower growers, and that those in low ground 
or "swales" are more subject than those on drier ground. Orchards 
should therefore be planted on well drained land, and should not be 
stimulated by too much water or too much fertilizer. 

Though all of the varieties of the pomaceous fruits are subject to 
this disease, as said before, some varieties have been found more 
subject to the attacks of blight than others. Of the apples, the crabs 
of all kinds have been found very prone to blight. Amongst the 
pear, in most places, the Anjou, Angouleme and Seckel are most re- 
sistant, Bartlet and Flemish Beauty are less so, while the Idaho, 
Clapp and Winter Nellis are very subject to blight. 

L. F. Henderson, Botanist. 



